1. Field of the Invention
The present invention relates to a system and method for detecting bone fragments and foreign materials in poultry and other meats. More specifically, the present invention relates to using x-ray imaging and laser imaging techniques to detect bone fragments, cartilage, etc, and other foreign materials in meats, particularly poultry fillets.
2. Description of Related Art
Physical contamination is one of the major types of contamination compromising food safety. In boneless poultry meat, physical hazards include plastic, metal, glass, bone fragments, etc., which can lead to serious injury if ingested by the consumer. To ensure food quality and food safety, it is necessary for poultry processors to inspect each piece of boneless poultry and to make sure that bone fragments and any other unwanted hazardous materials such as metals and plastics do not remain in the product.
X-ray imaging techniques, as noninvasive inspection methods, have been used for years to detect physical contamination in food products. However, traditional x-ray inspection systems currently being used to detect bone fragments in poultry fillets have a high rate of failure (over 30%). As suggested by numerous publications and industrial reports, x-ray inspection systems cannot succeed in detecting bone fragments in poultry unless the challenge of uneven meat thickness is addressed. Generally, the intensity (or grayscale) of an object in an x-ray image reflects the x-ray absorption, which is dictated by the physical characteristics of the material and its thickness. As such, traditional x-ray imaging detection technologies have significant difficulties in detecting food contaminations because of variations in food thickness.
One thickness cancellation method adopted by the industry is to press the meat mechanically. A pump is used to press the meat into a pipe, compressing it into a rectangular block of uniform thickness before it is scanned by an x-ray imager. It was reported that the method worked particularly well for ground meat inspection. However, for products such as poultry fillets, where the preservation of the natural shape is desired this compression method is unattractive due to the inevitable meat damage. Furthermore, once the X-ray machine reports a contamination in the pipe, it is often difficult for human inspectors to determine the exact location of the defect in the chunk of rejected meat.
Other than a single energy based x-ray imaging, dual x-ray imaging technology has also been investigated by researches due to its capability in differentiating the different materials based on their respective responses to different x-ray energy level. However, limitations of this dual energy method come from the underlying physics. Compared to the human body, poultry fillets are much thinner and softer, thus in order to have high quality x-ray images, it is necessary to use lower energies than those for medical radiography. This requirement implies that the difference between the high and low energies is small, which leads to an insufficient contrast between the images taken at the two energies.
Imaging technologies other than x-ray imaging have also been adopted by researches for detecting foreign material in food products. Laser irradiation imaging has been used in which a laser beam is used to scan food products. The presence of undesired ingredients can be determined when variations in the intensity of the laser beam passing through the food products are found. However, such systems also have a higher failure rate than desired, since they are not capable of capturing a true profile of the surface of a meat product due to undetected surface bumps or other hidden occlusions on the surface.